We are in the process of spec'ing out a system to virtualize our data center. We are looking at a 4 blade system with dual E5-2620 v4 (8 core) and 386 GB RAM per blade. During this process someone on our team suggested going to a single processor (E5-2683 v4 16 core) and same amount of memory. This would save us approx $25,000 on licensing of VMWare and Veeam (per processor licensing) when you consider a second identical setup for DR.
All the vendors don't want to spec out the single processor setup, but cannot give an exact reason why. We are trying to do our due diligence on this single proc idea since the saving would be considerable.
Can anyone give us a technical reason why we shouldn't go with single processor blades (e.g. performance) and why?
FYI - The blades would support 386 GB RAM in a single proc setup.
Hello venatorinc ,
I would say both are great options.However, this decision depends on the type of project you are planning to do.
Could you give us more details about the project you are planning to do?
Having dual processor options allow for a more powerful system and also provides a better virtualization experience. Regarding the performance, it will be considerably better because main processor will be aided by coprocessor which will be charged with the Virtualization tasks.
Please take into consideration that having more cores in a host server gives the hypervisor CPU scheduler more flexibility when trying to schedule CPU requests that are made by VMs. Having more cores available makes a CPU scheduler's job easier and improves VMs' performance on a host by being able to perform more instructions.
Generally, quad-core CPU's are recommended for virtual hosts for two reasons. The first reason is virtualization software is licensed by the number of sockets in a server and not the number of cores you have in that server, if you are planning on purchasing 8 core E5-2620 V4 processors that will be even better. Since you get more CPU's per license than you purchase in the virtualized environment (VMWare). The second reason is that having more cores in a host server gives the hypervisor CPU scheduler more flexibility as above mentioned.
This is the reason why it depends on the type of project you are planning. You could save money by using single processor options and take advantage of the multi-core options of the CPU(octa core).
Please let us know if you have any more questions.
Thank you for the reply. The project we are doing is virtualizing our entire data center which would include 1 Exchange server, 2 MS SQL servers, 8 terminal servers and a bunch of general purpose servers.
We had a study done on our environment to determine the utilization of our resources and help decide what would be needed to virtualize everything. We decided we would need 48 cores and around 1 Terabyte of usable memory.
We would have 4 hosts in an N +1 configuration (basically 3 usable). Each host would have 16 cores and 386 GB RAM. We originally were going to use 2 E5-2620 v4 (8 core) per host giving us the required 16 cores. Then what was suggested was using just 1 E5-2683 v4 (16 core) per host. So either setup gives us the same 16 cores per host. There will be a duplicate setup of 4 hosts in our disaster recovery site.
So the number of cores is not my question, it's the number of physical processors per host (2 vs 1).
Is there an advantage or disadvantage to having 1 processor instead of 2? Are there any bottlenecks in I/O, accessing memory or anything else?
Hello venatorinc ,
There are advantages of having 2 processors per host. At the QPI level, Accessing Memory, DMA. L2 cache, The way the s the hypervisor CPU scheduler assigns the jobs or tasks will be more flexible.